About Docker Compose Validator

Validate docker-compose.yml files with warnings and best practices. Part of the DevTools Surf developer suite. Browse more tools in the Developer Utilities collection.

Use Cases

• Validate a docker-compose.yml before committing to the repository
• Check for common mistakes like missing healthchecks on database services
• Verify that environment variable references are complete and consistent
• Audit compose files from third-party projects before running them locally

Tips

• The validator checks YAML syntax, service name conflicts, and volume mount paths in addition to docker-compose schema — paste the full file including version header
• Look for the 'depends_on vs healthcheck' warning: depends_on only waits for container start, not service readiness — use healthcheck for proper startup ordering
• Use the network configuration validator to ensure services that need to communicate are on the same custom network

Fun Facts

• Docker Compose originated as Fig, a Python tool created by Orchard in 2013. Docker acquired Orchard in 2014 and renamed Fig to Docker Compose. The tool's YAML format has become the de facto standard for multi-container development environment definition.
• Docker Compose v2 (released 2021) rewrote the tool in Go and integrated it as a Docker CLI plugin (docker compose instead of docker-compose). Compose v2 added profiles, improved secrets handling, and is the current recommended version.
• A 2022 survey by JetBrains found Docker Compose is used by 55% of developers for local development environments — significantly more than Kubernetes (25%) for the same purpose. The simplicity gap between the two explains the continued dominance of Compose for development.

FAQ

What is the depends_on limitation and how to work around it?

depends_on: [db] ensures the db container starts before the app container, but does not wait for the database to be ready to accept connections. The fix: add a healthcheck to the db service and set depends_on condition: service_healthy in the app service.

What is the difference between COPY and volume in Compose?

COPY in a Dockerfile embeds files into the image at build time. Volumes in Compose mount host directories or named volumes into the container at runtime. Use volumes for development (code changes reflect without rebuilding); use COPY for production images.

What version of the compose file format should I use?

Docker Compose v2 deprecated the version key — you no longer need 'version: 3'. Old v2/v3 syntax still works, but the format is unified in the current spec. Remove the version key for new files and use the current Compose Specification.